Composite and metal chemical processing operations are becoming more and more of a burden on industry because of the ever-stricter requirements, being made on the environmental disposition of compounds used in the operations and resulting effluents. Processing operations affected include those involving clothing, rugs and furnishings, as well as those of a more industrial nature such as involving the cleaning and treatment of metals, ceramics, plastics, semiconductors, optics and other materials. Often hazardous solvent or aqueous mixtures are used to carry out the cleaning process. This is often required since such strenuous processes such as etching, leaching, oxidizing, anodizing, or other harsh process is necessary to treat the object. This is becoming more prevalent in clean room operations where smaller parts are being manufactured requiring more thorough and consistent treatments such as in the medical, semiconductor, and microelectronics and optics areas. Processing liquids generally now require mixtures of solvents to be most effective and because of environmental and fire safety issues, the choice of solvents is often limited. Open systems are still the most commonly used, but their appeal is shrinking with increasing demands for worker safety and health. Open systems include such approaches as solvent vapor degreasing, solvent, semi-aqueous or aqueous ultrasonic cleaning bathes, cold or hot aqueous or solvent dip tanks and aqueous or solvent spray systems. These systems suffer from a number of shortcomings, among the most important of which are the contamination of the environment and the cost of constantly replenishing the non-recoverable solvents. In addition, the cost of equipment to contain the vapor and to properly dispose of the vapor and liquid waste is becoming more and more formidable. There is also a rise in the concern for workers health and safety. All these factors give rise to the need for a more safe and effective process for the treatment of materials with harsh chemicals.
Unfortunately, many of the environmentally safe solvents that could be used as a processing fluid have a low flash point and become a fire and explosion hazard if used in most of the open systems mentioned above. Simply covering these systems does not suffice to prevent fires since this equipment have moving mechanical and electrical parts that can produce electrical or static sparks igniting the solvent vapor-air mixtures. The net result is that these systems generally depend upon fire suppression systems to provide safety to the equipment. These systems act as an end of line fire prevention method and are not attractive to today's end users. The closed systems available on the market today attempt to combat these problems but have indifferent success. Generally these systems mix air with the flammable solvent and provide little more fire protection then the open systems being used.
Thus, conventional chemical processing systems have problems in the area of hazardous fire prevention. They are generally limited to operating with solvents with no or high flashpoint. When using flammable solvents, the process is often limited to low temperatures for fire safety purposes
A different approach is described here that avoids some of the problems of solvent processing. In this approach the processing solvent is exposed to only low-pressure environments in order to control and maintain oxygen level exposure to the solvent. Essentially the oxygen content at every stage and within every tank in the process is maintained at a concentration level where no fire or explosion could ignite or propagate. The method also provides for solvent recovery from the processing chamber and part thus preventing any solvent mixing with ambient air during or after part removal. The method will thus allow the usage of a wide variety of solvents for processing parts and provide for a more effective, safer process than presently available on the market today.